God planned man's salvation before the creation:
Ephesians 1:5 Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will,
Ephesians 1:11 In whom also we have obtained an inheritance, being predestinated according to the purpose of him who worketh all things after the counsel of his own will:
This does not mean God arbitrarily chooses who will be saved and who will not be. He has revealed that He wants all men to be saved:
1 Timothy 2:3 For this is good and acceptable in the sight of God our Saviour;
1 Timothy 2:4 Who will have all men to be saved, and to come unto the knowledge of the truth.
John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
2 Peter 3:9 The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance.
God knows the future and knows who will receive His offer of salvation; predestination is based on God's foreknowledge and has more to do with what the Christian is predestinated TO than WHO is predestinated. Predestination assures eternal salvation:
1 Peter 1:2 Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, unto obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied.
Romans 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.